1. Field of the Invention
The present invention relates to a sheet glass heating method, and more particularly to a method of heating a glass sheet for laminated glass.
2. Description of the Relevant Art
Laminated glass, which finds wide use as front windshields of automobiles, is manufactured by heating first and second glass sheets to be paired in a heating furnace, shaping and annealing the glass sheets, and then joining the glass sheets face to face. The glass sheets may be shaped by a press shaping process, a gravity shaping process, or a roller shaping process. The first and second glass sheets are joined face to face by adhesive bonding with an intermediate film as of polyvinyl butyral sandwiched therebetween.
When the first and second glass sheets are to be bonded to each other, it is necessary that they be of a bent configuration having substantially the same shape. Basically, the first and second glass sheets are heated under the same conditions in the heating furnace so that they are held at the same temperature To at the exit of the heating furnace. The first and second glass sheets are fed, alternately one by one, two by two, or three by three, into the heating furnace.
The first and second glass sheets, from which laminated glass is to be constructed, may not necessarily have the same characteristics, such as thicknesses, material properties, and colored conditions, at all times. For example, the first and second glass sheets may have different thicknesses, or the first glass sheet may be a colored transparent glass sheet whereas the second glass sheet may be a colorless transparent glass sheet. If the first and second glass sheets have such different characteristics, then they tend to be held at different temperatures To at the exit of the heating furnace. As a result, the first and second glass sheets may not be shaped desirably, and may not appropriately be bonded to each other after they are shaped and annealed.
The present invention has been made in an effort to effectively solve the aforesaid problems of the conventional method of heating glass sheets for laminated glass.